During 16-22 July INGEMMET and IGP reported that the eruption of Ubinas was continuing with gas-and-ash emissions reported most days. An explosion on 17 July, preceded by several days of banded tremor, generated an eruption column that rose 5 km above the summit and expelled incandescent blocks onto the flanks. More explosions on 19 and 21 produced eruption columns of gas-and-ash; the column on 19 July rose 2.8 km above the summit. Emissions and exhalations on 16, 18, and 22 July of gas-and-ash rose to 200-1800 m above the summit. Eruption columns and emissions drifted mostly E, NE, and SE. There were no significant emissions on 20 July. Ashfall was reported in various towns downwind of the plumes, in the areas of Querapi (4 km S), Ubinas (6.5 km SSE), Tonohaya (7 km SSE), San Miguel (10 km SE), Escacha, Yalahua, Lloque, and Sacuhaya.

Geological Summary. The truncated appearance of Ubinas, Perú's most active volcano, is a result of a 1.4-km-wide crater at the summit. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45°. The steep-walled, 150-m-deep summit crater contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one from about 1,000 years ago. Holocene lava flows are visible on the flanks, but activity documented since the 16th century has consisted of intermittent minor-to-moderate explosive eruptions.

Sources: Instituto Geofísico del Perú (IGP), Instituto Geológico Minero y Metalúrgico (INGEMMET), Buenos Aires Volcanic Ash Advisory Center (VAAC)